Comment by u1hcw9nx
1 day ago
Unlike marketing terms, "nm density" is actually useful measure.
It describes density measure where you can compare it to planar transistors from the 28-nanometer (28 nm) node around 2010 to 2011 and before. A "0.7 nm" node has equivalent transistor density as if we could have shrunk standard flat transistor node down to 0.7 nanometers.
Why not use something absolute, like nand-gates per volume?
Transistor density in units of MTr/mm. (Million Transistors per square mm) is also used. The formula is
MTr/mm = 0.6×(NAND2 Tr Count)/(NAND2 Cell Area) + 0.4×(Scan Flip Flop Tr Count)/(Scan Flip Flop Cell Area)
Why do you think it's not commonly used?
I am not a chip designer, doesn't area matter way more than volume? Vertical space is basically free; it's horizontal space that is at a huge premium.
Plus heat dissipation is a limiting factor, which scales with area.
Why is density any bit important? All I care about is the price per transistor, and the power usage(mostly gate charge and leakage current?).
Density does directly scale with both of those in the form of more chips per die (=> lower cost) and smaller capacitance (=> less dynamic power dissipation).
If you want to reduce "effectiveness" of some process down to a single number, then density is far from the worst metric to pick.
Why is that all you care about? Stepping down a node gets you dramatically improved timing and design feasibility. The reduced density means you can pack the same design into less area. Your most challenging timing paths now have to traverse a shorter distance, and you can fit more of them relative to certain node-size invariant structures
isn't density a way to lower both the price and energy dissipation (so better heat management & energy efficiency)?
[flagged]
Yeah, the actual sizes are right there in the pictures, and never < 1 nm.
Density is mass per volume so how are you comparing it to a planar transistor? Your units don't even match.
All "density" means is that it's a quotient; I use spectral densities daily and that's "count per Hertz" which weirdly enough works out in normal units to be seconds.
Not all densities is mass per volume. eg. population density.
It's a physical quantity per some unit of spatial measurement so the units still don't match up b/c in one case the transistors are stacked per volume & in the other case per area.
> Historically, "node" sizes (like 28nm or 7nm) directly correlated to the physical length of a transistor's gate. Today, names like 3nm or 2nm reflect a marketing generation. The actual transistors are significantly larger than these nanometer labels, meaning density varies between companies
> Research organizations like IEEE have proposed new metrics, such as transistors per cubic millimeter (MTr/mm^3), to accurately map future 3D scaling. However, commercial chip foundries resist this change because it would make it harder to calculate commercial yields and thermal density limits using standard industry formulas.
https://share.google/aimode/Z5BqUjlZWFNphm6Z6
6 replies →
Population density isn’t planar, eg, why cities are denser than towns: their centers are more than 2D.
4 replies →
density is quantity per unit measure.
mass per volume is one example.
Density is this reply.
https://en.wikipedia.org/wiki/Transistor_count#Transistor_de...